Exoplanetology: Exoplanets & Exomoons

Aggregate Cloud Particle Effects in Exoplanet Atmospheres

By Keith Cowing
Status Report
astro-ph.EP
August 22, 2024
Filed under , , , , ,
Aggregate Cloud Particle Effects in Exoplanet Atmospheres
Left: Temperature-pressure profiles for a suite of irradiated hot atmospheres, from the EGP+ model suite (Fortney et al. 2008) to demonstrate the parameter space. Right: Corresponding eddy diffusivities Kzz for the various atmospheres using the methods of Saumon & Marley (2008). All models are solar metallicity. The upper part of the atmosphere where Kzz reaches a minimum and then increases as the inverse of the gas density is highlighted for the coolest atmosphere (green line) as the grey chalked line. We assume aerosol transport via Brownian motion above this region where Kzz transitions to nearly isothermal, the exact pressure of which depends on the specific temperature structure. — astro-ph.EP

Aerosol opacity has emerged as a critical factor controlling transmission and emission spectra. We provide a simple guideline for the effects of aerosol morphology on opacity and residence time in the atmosphere, as it pertains to transit observations, particularly those with flat spectra due to high altitude aerosols.

This framework can be used for understanding complex cloud and haze particle properties before getting into detailed microphysical modeling. We consider high altitude aerosols to be composed of large fluffy particles that can have large residence times in the atmosphere and influence the deposition of stellar flux and/or the emergence of thermal emission in a different way than compact droplet particles, as generally modeled to date for extrasolar planetary atmospheres.

We demonstrate the important influence of aggregate particle porosity and composition on the extent of the wavelength independent regime. We also consider how such fluffy particles reach such high altitudes and conclude that the most likely scenario is their local production at high altitudes via UV bombardment and subsequent blanketing of the atmosphere, rather than some mechanism of lofting or transport from the lower atmosphere.

Sanaz Vahidinia, Sarah E. Moran, Mark S. Marley, Jeff N. Cuzzi

Comments: 29 pages, 20 figures, accepted for publication in PASP
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2408.11215 [astro-ph.EP] (or arXiv:2408.11215v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2408.11215
Focus to learn more
Submission history
From: Sarah Moran
[v1] Tue, 20 Aug 2024 22:23:08 UTC (5,581 KB)
https://arxiv.org/abs/2408.11215

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

Follow on Twitter
MORE FROM Exoplanetology: Exoplanets & Exomoons